Rails 3 very long, very slow form - ruby-on-rails

Question

I have a very long form with nested form fields. It takes 30 seconds in development to load.
I've used a separate model for each drop down menu that I need - I don't know if that's such a good idea now that I have 35 of them. I also have 11 accepts_nested_attributes_for/ cocoon gem partials, which is super once the page has loaded, but I suspect the 11 different partials are slowing things down.
I'm caching the page which helps, and in production it's a lot quicker - 8 seconds - but still not really acceptable.
How should I ideally structure this long form? I can't think it's RESTful to split up an edit / update method. Or if the structure is OK, what can I do to improve performance? Like I say I'm caching, and there are no finds in the view. The controller is pretty regular although there's lots of calculations in methods in the model.
Here's a fragment. Many thanks in advance for any thoughts.
%a{:name => "Measurements"}
- f.inputs :name => "Measurements", :id => "main" do
%li.tip
= tooltip(:descriptivedetail_productcomposition_productcomposition, :hover)
= f.input :descriptivedetail_productcomposition_productcomposition, :label => "Product composition", :as => :select, :collection => Productcomp.all, :value_method => :code
%li.list
= link_to "Edit list", productcomps_path
%br
%li.tip
= tooltip(:descriptivedetail_productcomposition_productform, :hover)
= f.input :descriptivedetail_productcomposition_productform, :label => "Product form", :as => :select, :collection => Productform.all, :value_method => :code
%li.list
= link_to "Edit list", productforms_path
%br
%li.tip
= tooltip(:descriptivedetail_primarycontenttype, :hover)
= f.input :descriptivedetail_primarycontenttype, :label => "Content type", :as => :select, :collection => Contenttype.all, :value_method => :code
%li.list
= link_to "Edit list", contenttypes_path
%br
%li.tip
= link_to_add_association 'Add measurement', f, :measurements
= f.semantic_fields_for :measurements do |measurement|
= render 'measurement_fields', :f => measurement
%br
%li.tip
= link_to_add_association 'Add extent', f, :extents
= f.semantic_fields_for :extents do |extent|
= render 'extent_fields', :f => extent
%br
%a{:name => "Supply"}
- f.inputs :name => "Supply", :id => "main" do
%li.tip
= link_to_add_association 'Add supply info', f, :supplies
= f.semantic_fields_for :supplies do |supply|
= render 'supply_fields', :f => supply
%br
%a{:name => "Rights"}
- f.inputs :name => "Rights", :id => "main" do
%li.tip
= link_to_add_association 'Add rights info', f, :rights
= f.semantic_fields_for :rights do |right|
= render 'right_fields', :f => right
%br
%a{:name => "Related"}
- f.inputs :name => "Related", :id => "main" do
%li.tip
= link_to_add_association 'Add related product info', f, :relatedproducts
= f.semantic_fields_for :relatedproducts do |relatedproduct|
= render 'relatedproduct_fields', :f => relatedproduct
%br
An example partial:
.nested-fields
= f.inputs do
%br
%li.tip
= tooltip(:descriptivedetail_measure_measuretype, :hover)
= f.input :descriptivedetail_measure_measuretype, :label => "Measure type", :as => :select, :collection => Measuretype.all, :value_method => :code
%li.list
= link_to "Edit list", measuretypes_path
%br
%li.tip
= tooltip(:descriptivedetail_measure_measurement, :hover)
= f.input :descriptivedetail_measure_measurement, :label => "Measurement"
%li.tip
.links
%br
%li.tip
= tooltip(:descriptivedetail_measure_measureunitcode, :hover)
= f.input :descriptivedetail_measure_measureunitcode, :label => "Unit", :as => :select, :collection => Measureunit.all, :value_method => :code
%li.list
= link_to "Edit list", measureunits_path
%br
= link_to_remove_association "Remove measurement", f